Hydrodynamic tapered roller bearings and gas turbine engine systems involving such bearings

ABSTRACT

Tapered roller bearings and gas turbine engine systems involving such bearings are provided. In this regard, a representative bearing cage for a gas turbine engine includes: an outer cage rim and an inner cage rim; the outer cage rim having a rounded edge at a location of contact between the outer cage rim and a roller.

REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. Ser. No.12/036,581, which was filed on Feb. 25, 2011 now U.S. Pat. No.8,235,599.

BACKGROUND

1. Technical Field

The disclosure generally relates to bearings.

2. Description of the Related Art

Various mechanical systems, such as gas turbine engines, utilize rollerbearings. By way of example, roller bearings are utilized in a gasturbine engine to support a turbine shaft.

Notably, wear of a roller against a bearing inner race face can be asignificant issue. By way of example, resultant forces from the bearingradial load with thrust and centrifugal loads press the roller againstthe bearing inner race flange resulting in friction and wear. Therelative rotational motion between rollers and a bearing inner race endflange also results in contact sliding that tends to degrade bearingperformance.

SUMMARY

Tapered roller bearings and gas turbine engine systems involving suchbearings are provided. In this regard, an exemplary embodiment of abearing cage for a tapered roller bearing having rollers comprises: anouter cage rim and an inner cage rim; the outer cage rim having arounded edge at a location of contact between the outer cage rim and aroller. An exemplary embodiment of a bearing assembly comprises: aplurality of rollers, each of the rollers having an end; and a bearingcage operative to contain the plurality of rollers, the bearing cagehaving an outer cage rim, the outer cage rim having a rounded edge at alocation of contact between the outer cage rim and first end of a firstof the rollers.

An exemplary embodiment of a gas turbine engine comprises a compressor;a shaft interconnected with the compressor; a turbine operative to drivethe shaft; and a bearing assembly operative to support to the shaft, thebearing assembly having a plurality of rollers, a race and a bearingcage operative to contain the plurality of rollers, the bearing cagehaving a cage rim, the cage rim of the bearing cage being operative todirect load imparted via the rollers to the race.

Other systems, methods, features and/or advantages of this disclosurewill be or may become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features and/oradvantages be included within this description and be within the scopeof the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with referenceto the following drawings. The components in the drawings are notnecessarily to scale. Moreover, in the drawings, like reference numeralsdesignate corresponding parts throughout the several views.

FIG. 1 is a schematic diagram depicting an exemplary embodiment of a gasturbine engine.

FIG. 2 is a schematic diagram depicting an exemplary embodiment of ahydrodynamic tapered bearing assembly.

FIG. 3 is a perspective diagram depicting a portion of the hydrodynamictapered bearing assembly of FIG. 2.

FIG. 4 is a perspective diagram depicting another portion of thehydrodynamic tapered bearing assembly of FIG. 2.

DETAILED DESCRIPTION

Tapered roller bearings and gas turbine engine systems involving suchbearings are provided, several exemplary embodiments of which will bedescribed in detail. In this regard, some embodiments involve the use ofa bearing cage that limits contact of the cage to locations on theroller ends that exhibit reduce motion relative to the cage. As such,friction between the cage and the rollers can be reduced. Notably,various applications of the bearings can involve gas turbine enginesystems.

Reference is now made to the schematic diagram of FIG. 1, which depictsan exemplary embodiment of a gas turbine engine utilizing an embodimentof a hydrodynamic tapered roller bearing. As shown in FIG. 1, engine 100is depicted as a turbofan gas turbine engine that incorporates a fan102, a compressor section 104, a combustion section 106 and a turbinesection 108. Although depicted as a turbofan gas turbine engine, itshould be understood that the concepts described herein are not limitedto use with turbofans or other types of gas turbine engines as theteachings may be applied to other types of engines or other mechanicalsystems that incorporate tapered roller bearings.

In FIG. 1, tapered roller bearing 110 is utilized in gas turbine engine100 to support turbine shaft 112. Notably, tapered roller bearings, suchas bearing 110, can be utilized in gas turbine engine 100 to carry bothradial and axial loads simultaneously.

As is known, there is an ongoing challenge to maintain the integrity ofa tapered roller bearing. In this regard, reference is made to theschematic diagram of FIG. 2, which depicts an exemplary embodiment of atapered roller bearing assembly 200. Bearing assembly 200 incorporatesmultiple rollers (e.g., a roller 250) that are held by a bearing cage238, which includes an outer cage rim 240 and an inner cage rim 242. Therollers run about a longitudinal axis 202 between the outer raceway 212of an outer race 210 and the inner raceway 222 of an inner race 220. Theinner race 210 also includes an inner race flange 230 that defines anaxially disposed annular surface 231 and a radially disposed annularsurface 233.

In known tapered roller bearings, wear of a roller 250 against a bearinginner raceway 222 can be a significant issue. By way of example, in andaround a location generally corresponding to area 260 in a known taperedroller bearing, resultant forces from the bearing radial load incombination with thrust and centrifugal loads tend to press the rollersagainst the inner race flange, thereby creating friction and resultingin wear. The relative rotational motion between the rollers and innerrace flange also results in contact sliding. Bearing assembly 200,however, is configured to reduce or eliminate this wear and contactsliding.

Bearing assembly 200 includes a bearing cage configured to reduce thiswear and/or contact sliding by using outer cage rim 240 to transfer loadfrom the vicinity of area 260 to the inner race flange 230. Additionallyor alternatively, wear and/or sliding contact can be reduced by outercage rim 240 contacting each roller at a location of reduced relativemotion. That is, contact between the outer cage rim and the roller isprovided at an outer axial end of longitudinal axis of each roller(e.g., at location 255 of axis 252 of roller 250), the theoretical pointof zero relative velocity between outer cage rim and roller. In thisembodiment, the outer cage rim 240 incorporates a rounded edge 254 at apoint of contact between the outer cage rim 240 and roller end 250 toreduce the degree of contact between the roller end 250 and the outercage rim 240.

The outer cage rim 240 is shaped to direct the axial load path throughthe bearing cage rims 240, 242. By way of example, the outer cage rim240 is generally L-shaped (in cross sectional view), incorporating anaxially disposed annular surface 241 and a radially disposed annularsurface 243. Such a configuration provides alignment with inner raceflange 230 along, for example, line 236 both axially and radially.

In the embodiment of FIG. 2, bearing assembly 200 is lubricated by oil.This embodiment also incorporates optional hydrodynamic features. Inthis regard, inner race flange 230 includes a recess area 232 to providelubrication oil to various surfaces of bearing assembly 200. Notably,inner race flange 230 includes a plurality of channels 234 fordistribution of oil sourced from the recess area 232. By way of example,the oil lubricates the point of contact 254 between the edge of outercage rim 240 and roller 250. At point of contact 254, there exists a lowresultant relative difference in contact speed between the outer cagerim 240 and the roller 250, creating a theoretical point of zerorelative velocity. This tends to reduce friction and wear between therollers and inner race flange 230 as compared with conventionalconfigurations in which those surfaces are in direct contact with eachother (location 260).

In this regard, reference is made to the schematic diagram of FIG. 3,which depicts a portion of bearing assembly 200. In particular, surface231 of inner race flange 230 includes multiple lobes (e.g., lobe 306) tofurther enhance loading stability. The multiple lobes are located, forexample, in an equally spaced apart fashion along surface 231. In thisembodiment, each of the lobes extends radially along surface 231 and isconfigured to interact with surface 241 of the outer cage rim 240. Inthis embodiment, three such lobes are used, with the lobes beingseparated from one another by an angle of approximately 120 degrees. Inother embodiments, various other numbers and spacing of lobes can beused. Notably, the number of lobes can be varied to affect loadingstability, for example.

In operation, oil is circulated in bearing assembly 200 from recess area234 through the inner race flange 230. The oil flow, as shown by arrows302, routes through channels 234 to the top and inner side of the innerrace flange 230 for contact with the outer cage rim 230 and theremainder of the bearing assembly 200. Each lobe operates as a wedgethat affects hydrodynamic loading capacity. The number of channels 234and the placement of the channels 234 in the inner race flange 230 canbe varied to affect oil flow and loading stability, for example.

Lobes can be varied in size in radial, axial and/or circumferentialdirections to affect loading stability. Variation in size of the lobesaffects oil flow and the volume of oil that can be delivered into eachlocation of the bearing assembly 200, thus affecting loading stabilityof the bearing assembly 200.

Reference is made to the schematic diagram of FIG. 4, which depictsmultiple lobes located on surface 233 for increased hydrodynamic loadingstability. As shown in FIG. 4, the lobes (e.g., lobe 402) on surface 233are configured to interact with surface 243 of the outer cage rim 240.As shown, the lobes are circumferentially separated from one another byan angle 406 of approximately 120 degrees. The lobes 402 can vary insize in radial, axial and/or circumferential directions to affectloading stability.

In summary, the bearing axial load path is re-directed through the outercage rim to the inner race flange (surface 231) that acts as ahydrodynamic thrust bearing. In the case of thrust reversal duringoperation, the same concept could be applied to the roller endcorresponding to the inner cage rim, resulting in tapered roller bearingwith double hydrodynamic thrust bearing faces.

It should be emphasized that the above-described embodiments are merelypossible examples of implementations set forth for a clear understandingof the principles of this disclosure. Many variations and modificationsmay be made to the above-described embodiments without departingsubstantially from the spirit and principles of the disclosure. By wayof example, although the lobes of the bearing assembly have beendescribed herein as being associated with the inner race flange, one ormore of the lobes can be located on a bearing cage. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the accompanying claims.

1. A bearing for contacting a roller, said bearing comprising: a bodyhaving an axial forward end and an axial rearward end, said axialforward end having a rim portion having a rounded edge for engaging saidroller that rotates about an axis, said rim portion being disposedperpendicularly to said axis, wherein said axial forward end and saidaxial rearward end cause said body to form an L-shape cross-sectionwherein a portion of said axial forward end is angled relative to saidrim portion.
 2. The bearing of claim 1, wherein said portion and saidaxial rearward end are parallel.
 3. The bearing of claim 1, wherein saidrim is for attaching to said bearing radially inwardly of said axisonly.
 4. The bearing of claim 1, wherein the rim portion has a radiallydisposed annular surface operative to direct a load imparted to an outerrim via the roller.
 5. The bearing of claim 1, wherein the rim portionhas an axially disposed annular surface operative to direct a loadimparted to an outer rim via said roller.
 6. The bearing cage of claim1, wherein said rim portion is attached to a hydrodynamic tapered rollerbearing cage.
 7. A first bearing for supporting a second bearing, saidfirst bearing comprising: a body having an axial forward end and anaxial rearward end, said axial forward end having a rim portion having arounded edge for engaging said second bearing that rotates about anaxis, said rim portion being disposed perpendicularly to said axis,wherein said axial forward end and said axial rearward end cause saidbody to form an L-shape wherein a portion of said axial forward end isangled relative to said rim portion.